On one hand, the fact Sakurai mentioned he wants to please the fans is a good sign for us (and well, also for big loud fanbases like Geno, Sora, Lloyd, etc..). Isaac has (or had) one of the most vocal and popular fanbase in the internet, being in top of a lot of polls before his reveal as an AT. Also, an hypothetical Golden Sun game could be in the works (at least the posibility is there) and that would help a lot.
But, on the other hand, that statement could mean nothing. Basically, any character will please the fans, even if they're obscure. We have the last one, Terry, as an example. Very few people asked for him and, even if some people claim he's popular in latinoamerica and some parts of Asia, I really doubt that that market is important for Nintendo when they don't even distribute their console and games themselves. Even Piranha Plant was well-received after some time... And seeing how all the characters from the season pass are 3rd parties (I really doubt the 5th will be a 1st party...), I can't think they will change it in the new DLCs.
Besides, the competition is still terrible, there are a lot of characters there which can be eligible, even for the first party, and now all the AT and spirits are also a competitors. Probably the only ones who are "deconfirmed" are the last paid Mii costumes lol
Even if our probabilities has increased a bit due to announcement, nothing is guaranteed. Being an AT really hurts, but I hope the tantrum we had when it was announced help us. If that leak from ¿Papagenos? was true, at least Nintendo is aware of demand, which help us a lot and can put above of others. But nowadays, people can support other options for the fact they see Isaac as an imposible for his current role. If one character can break the rule "an AT can't be a playable character in the same game", that would help, because people will jump in Isaac ship's again (well, if he isn't the first one to break the rule).